Thermostatic element



1386- 1934- N. L. DERBY THERMOSTATIC ELEMENT Filed Aug. 25, 1951 2 sheets -sne-st l I J- l J 87 rm/van INVENTOR 9 1934- N. L. DERBY THERMOSTATIC ELEMENT 2 Sheets-Sheet 2 Filed Aug. 25, 1951 #M m FXR C k m I m m w. 2 w m c F. 2

5 WW w 2 RM" m m" n "m 'IIIIIII Patented D... 4, 1934 1,983,269.

UNITED STATES PATENTOFFICE 1,983,269 'rHERMos'rA'rio ELEMENT Norman L. Derby, Jackson Heights, N. Y. Application August 25, 1931, Serial No. 559,186 16 Claims. (Cl. 297-111) This invention relates to thermostatic elements pound ingot built up from aseries of cupped composed of metallic members joined together washers; and makes use of principles of, and comprises Fig. 14 is. an end view of the ingot shown in improvements on the invention of my copending Fig. 13; n application Serial No. 492,707, filed November 1, Fig. is a vertical sectional elevation of a 1930. p thermostatic bellows element made from the ingot The general object of the present invention is shown'in Fig. 7; and 'to provide a hollow thermostatic element which Fig. 16 is an inverted plan view of part of may take various forms, but each of which comthe bellows shown in Fig. 15. l0 prises curved portions formed of layers of metals The thermostatic element shown in Figs. 1 5 having different coefiicients of expansion and so and 2 is in the form of a bent tube 12 having one arranged as to cause the elements to deflect or end 11 fixed, and its opposite end 10 free to move. change in form and dimensions in a novel and As shown, the longitudinal axis of the free end effective manner, in response to changes in the 10 is at right angles to the longitudinal axis of l5 temperatures to which the element is subjected. the stationary end 11. The tube end portions 10 7 In the accompanying drawings: and 11 are circular in shape andare fitted with Fig. l-is a side elevation of a thermostatic elereinforcing washers l3 and M, respectively. ment in the form of a curved tube which straight- However, the free end 10 may be completely ens or increases its curvature as its temperature closed by a circular disc. As shown, the washer 2b is increased or diminished; 14 surrounds a stationary nipple 9 by which the Fig. 2 is a transverse section on'the line 2--2 thermostatic element is supported. In its cold of Fig. 1; condition, the body portion of the tube 12 is of Fig. 3 is a perspective view of a portion of a theelliptical cross section shown in Fig. 2. compound tubular ingot composed of two metals The element shown in Figs. 1 and 2 may be 25 from which the thermostatic element shown in formed from the compound tubular'ingot shown Figs. 1 and 2 may be made; in Fig. 3 by suitably reducing the thickness of Fig. i is a perspective view of a portion of a the ingot to form a tube of circular cross seccompound tubular ingot, composed of three diition and then flattening and bending the body ierent metals, suitable iormalring tubular thermoportion of the tube, so that in its cold condition,

.30 static elements generally similar to that shown in the body portion will have the cross section .Figs. 1 and 2; shown in Fig. 2, and the tubular elementwill Fig. 5 is an elevation partly in section of a have the longitudinal curvature shown in Fig. l, thermostatic element in the form of a helically the long diameter of the elliptical section being corrugated tube; parallel to the axis of longitudinal curvature of 35 Fig. 6 is a longitudinal elevation, partly in secthe element. The ingot shown in Fig. 3 com- 90 tion, of a tubular ingot having helically wound prises a tubular body portion 2 of a metal as external and internal inserts; brass having a relatively high coeficient of Fig. 7 is a longitudinal elevation partly in secthermal expansion and formed with diametrally tion of a tubular ingot similar to that shown in opposed longitudinal extending recesses in its all Fig. 6 except that the inserts are parallel to a periphery in which are secured longitudinal inplane at right angles to the longitudinal axis of' sorts 5 of a metal as invar having a relatively the tubular ingot; low co-eificient of thermal expansion, and- Fig. 8 is a section on the line 8-8 of Fig. 7 formed with diametrally opposed longitudinal Fig. 9 is a longitudinal elevation partly in secextending recesses in its inner wall, alternating 45 tion or a compound tubular ingot containing about the axis of-the ingot with the recesses first three different metals; referred to and in which are similarly secured Fig. 10 is an end elevation of the compound longitudinal extending inserts 5 of invar, or the ingot shown in Fig. 9; like metal having a low coeflicient of thermal ex- Fig. ll is a longitudinal elevation of a compa The p p y of t ingot is thus d 50- pound ingot suitable for making a bellows, built vided circumferentially into four equal segments up of recessed washers of one metal and rings of of which two of brass or the like alternate with another metal; two of invar or the like, the outer surface of the Fig. 12 is'an end elevation of the ingot shown segments being flush. The inner curved surface in Fig. 11; of the ingot is similarly formed of four segments, 55 Fig. 13 is a longitudinal elevation of a comtwo of brass or the like and two of invar. In

I at the ends of the long axis of the elliptical secindicator.

tion are formed of invar. When the tubular element shown in Figs. 1 and 2 is heated, the relative expansion of the brass segments relative to the invar segments tends to change the elliptical cross section of the body portion shown in Fig. 2 to one more nearly circular, with the result that the longitudinal curvature of the element will diminish and the element will deflect from its full line position toward the dotted line position shown in Fig. 1. The greater the temperature change the more nearly circular the cross section of the portion of the tube becomes,

and therefore, the greater the deflection. The action of the element is thus similar to that of a Bourdon tube, but is due to temperature changes and not to fluid pressure variations. If the temperature increase is suflicient to make the cross section of the body portion of the element circular, or approximately so, the element will assume a position intermediate its -full and dotted line positions shown in Fig. 1

which is determined by the relative lengths of the concave and convex sides of the element. On cooling, the element will regain its original bent shape and elliptical cross section.

It is also possible to reverse the action of such an element as is shown in Figs. 1 and 2, so that the longitudinal curvature of the element will be increased by heating" the element above its cold temperature. Thus, if the element shown in Figs. 1 and 2, while heated to a relatively-high temperature and without altering the position of its stationary end 11, as shown in Fig. 1, is permanently bent parallel to a plane at right angles to the plane of Fig. 1, and at the same time the body portion 2 of the element be given a permanently elliptical cross section with the long diameter of the ellipse at right angles to the long diameter of the element as shown in Figs. 1 and 2, the body portion of the element thus formed will tend to reduce its longitudinal curvature and to approach the circular cross section when the element cools down.

- A tubular element as shown in Figs. 1 and 2 may be used as a power unit or as a temperature It may also be arranged to indicate the temperature differential between a fluid inside the tube and another fluid exposed to the outside of the tube, as for instance,'in devices for measuring or controlling the humidity in a chamber.

' the outer and inner invar strips 5 being relatively disposed about the axis of the ingot as are the invar strips 5 of Fig. 3. Between the outer invar strips 5,- two longitudinal stripsof brass 2' are secured to the outer side of the shell 1 between the outer invar strips 5, and two longitudinal strips of brass 2' are secured to the inner side of the shell 1 between the inner invar strips 5. As everdur, like brass and unlike invar, has a substantial thermal coemcient of expansion, a thermostatic element of the form shown in Figs,

1 and 2, with the outer invar strips intersected by the long axis of the elliptical section of the body portion of the element will change in respect to its longitudinal curvature and the cross sectional shape of its body portion in response to changes in temperature as does the element shown in Figs. 1 and 2.

In Figs. 7 and 8 is represented a compound tubular-ingot which when die drawn longitudinally will be suitable for making corrugated thermostatic tubing as shown in Figs. 15 and 16. The ingot shown in Figs. 7 and 8 comprises a tubular center member 1A of high expansion metal like brass, having a series of outside and inside longitudinal ribs or projections 2A and 3A, respectively. The said projections form rings extending circularly about the longitudinal axis of the ingot, the sides of said rings being generally parallel to planes transverse to the longitudinal axis of the tube. The space between each adjacent pair of projections 2 is filled by a curved strip 5A of invar with its two ends 20 abutting as shown in Fig. 8, and the space between each.

pair of projections 3A is similarly filled by a curved strip 5A of invar having abutting ends 21. After the invar strips 5A and 5A have been inserted in the corresponding spaces, they are. permanently joined to the walls of the projec-- tions, and to the body center member 1A. After the compound tubular ingot thus formed is drawn through a series of dies until it has acquired the desired reduction of wall thickness, the ingot may be given the corrugated form shown in Figs. 15-

and 16 by any means now in general use for making deeply corrugated thin walled tubing. With the invar at the concave sides of the corrugation curves and brass at their convex sides as shown in Figs. 15 and 16, the element will shorten when heated and elongate when cooled. As shown,

one end of the corrugated element is secured to is die drawn and corrugated as in the case of the' ingot shown in Figs. 7 and 8, but the corrugated thermostatic tube thus formed,.which is shown in Fig. 5, will have helical corrugations instead of the straight corrugations shown in Fig. 15.

Figs. 9 and 10 are longitudinal and side elevations, respectively, of a trimetaliic tube suitable when drawn down, to make corrugated tubing generally similar to that shown in Figs. 15 and 16. The ingot shown in Figs. 9 and 19, consists of a center tubular shell of everdur, and alternating rings 20 and 50 of brass and invar, respectively, joined to the outer wall surface of the everdur shell, and alternating rings 2C and 50' of brass and invar, respectively, joined to the inner wall surface of the everdur shell. The inner and outer rings are staggered so that any portion of the ingot showing brass at its outer surface will show invar at the inside surface.

Figs. 11 and 12 show a compound tubular ingot composed of circular sections 2D of high exring 5D of invar fitting on said hub section.

The brass and invar members after being assembled and joined into a unitary structure may be drawn down and corrugated to form an element of the general character shown in Figs. 15 and 16.

Figs. 13 and 14 show a compound tubular ingot composed of cupped annular laminations 2E of brass, alternating withsimilar laminations 5E of invar, the projecting hub of one lamination fitting in the" recess in an adjacent lamination. The laminations when joined together with a binder into a unitary structure may be die drawn longitudinally and corrugated to form a thermostatic element like that shown in Figs. 15 and 16. At the ends of the ingot are invar ring laminations 5E and 5E" specially formed to give the ingot flat end surfaces.

In the construction of the compound tubular ingots suitable formaking thermostatic elements as herein described, itis to be understood that wherever surfaces of two members come together,

they are to be permanently joined'along their contacting surfaces.

.In one method of securing inserts of invar between rigidly connected projection orribs of brass, the parts are thoroughly pickled and cleaned to remove all foreign matter. Next, the parts to be joined together are-moistened and then covered with a thin layer of flux such as powdered borax. The strips of invar are then placed in the spaces between adjacent brass ribs or projections with a thin sheet of silver solder, having a .melting' temperature of about 1600 F., interposed between the contacting surfaces. When the sides of the projecting legs and invar strips are slightly tapered it is' preferable to tack the sheets of silver solder onto the invar strips by spot welding and then force the strips into the spaces in the brass while the brass is at a temperature of approximately 500 F. Then after the compound in-.

got is allowed to cool down to room temperature, it is clamped in a heat resisting vise which exerts considerable pressure to prevent lateral expansion of the spaces holding the invar, when the ingot is again heated. Next the compound ingot clamped in the vise is placed in the furnace and heated slightly abovethe melting temperature of the solder. The ingot is then allowed to cool down slowly while still in the furnace, to prevent undue oxidation of the members. After cooling the ingot is rolled down to the thermostatic element thickness desired, which may be two or three hundredths of an inch in some cases.

In my said prior application, Ser. No. 492,707, filed November 1, 1930, I have'described other methods of manufacturing ingots and the production of bimetallic thermostatic metal there from of a suitable thickness, for example, of a thickness of two or three hundredthsof an inch, which may be followed in the manufacture of any of the ingots and elements described herein.

Any of several other metals may be used in place of brass as the high expansion metal in the ingots and elements previously described herein as including brass portions with invar used in each case as the low expansion metal. stance, I may use nichrome steel as the high expansion metal'in making bimetallic elements for use at high temperature, and may-join it to the -asthe high expansion metal in lieu of brass in the arrangement heretofore described, and may For in' join it to the invar with silver solder, using as 'a flux fused borax and 10% sodium fluoride. Furthermore, everdur may be fused into grooves in an invar slab to make bimetallic elements by automatic carbon arc. welding of the type known as the" Electronic Tornade system, produced by the Lincoln Electric Company.

In making a trimetallic ingot such as that shown' in Figs. 4 or 9,- various other metals besides everdur may be used for the center member, however it is preferable to use a metal having a coefiicient of heat expansion approximately the same astherhigh expansion strips joined. The thermostatic elementsare more sensitive when the high expansion metal thickness is slightly thicker than the low expansion metal thickness, and in the drawings an effort has been made in every case to show a brass thickness greater than the invar thickness.

What I claim and desire to secure 'by Letters Patent is:

1. A hollow thermostatic element the wall of which comprises a center member having spaced projecting members extending therefrom, and members having a different coeflicient of heat expansion than said projecting members filling spaces between said projecting memberss V 2. A hollow thermostatic element the wall of which comprises a center member having projecting members extending from opposite faces thereof, and members having a different coeflicient of heat expansion than said projectin members permanently positioned between adjacent projecting members.

3. A hollow thermostatic element the wall of which is' composed of aseries of portions each including inner and outer layers of different materials, the outer layer material in each of some of said portions having a greater coefiicient of expansion than the corresponding inner layer material, and respectively adjacent portions of said wall having outer layer material with a smaller coeflicient of expansion than that of the inner layer material.

4. A hollow thermostatic element, the wall of ing one coeflicient of expansion and an inner layer of material having a different c'oeilicient of thermal expansion.

5. A hollow thermostatic element, the wall of which comprises a set of portions more externally convex than the portions of another set adjacent thereto, each of said portions comprising an outer layer of material having one coefficient of expansion and an' irmer layer of material having a different coeflicient of expansion, the layer having the higher coefficient being at the inner side of the element in the said. portions of one set and at the outer side of the element in the said portions of the other set.

6. A thermostatic element in the form of a circumferentially complete section of a tube and comprising a curved wall portion extending part way about the tube axis and including an inner pansion, the inner layer coeflicient being greater in one or more portions and less in one or more other portions than the corresponding outer layer coefilcient.

8. A thermostatic element in the form of a secti n of a tube with opposite sides flattened and each including an inner layer of material having one coeflicient of expansion and an outer layer of material having a higher coefficient of expansion.

9. A thermostatic element in the form of a section 0 a tube with an opposin pair of sides more sh 1y curved than the intervening sides and each of said opposite pair of sides including an inner layer of material having one coefficient of expansion and an outer layer of material having a smaller coeflicient of expansion.

10. A thermostatic element in the form of a section of a tube the wall of which comprises inner and outer layers each of which includes a circumferential series of curved portions with adjacent portions of each series formed of materials having, diflerent coefficients of expansion and with the juxtaposed inner and outer layer portions formed of materials having different coeflicients of expansion.

11. A thermostatic element in the form of a tube bent into an arc and having the portions of its wall at the inner and outer sides of the arc and the remaining wall portions each formed with inner and outer layers of materials having different coeflicients of expansion, the coeificient of expansion of the outer layer material being greater in the first mentioned portions, and less in said intervening portions than the coefllcient of expansion of the corresponding inner layer material.

12. A thermostatic element in the form ofa tube bent into an arc and having portions of its wall at the innerand outer sides of said are connected by intervening wall portions, each of the latter of which comprises inner and outer layers of materials having respectively larger and small er coefficients of expansion.

13. A thermostatic element consisting of a curved tube having its convex and concave sides,

flattened and each formed with inner and outer layers'of materials having different coeflicients of expansion, the two inner layers forming portions of the iimer surface of the tube and the. two outer layers forming portions of the outer surface of the tube and the two layers forming portions of one of said surfaces having coefficients of expan-.

sion greater than those of the respectively adjacent layers forming portions of the other of said surfaces.

14. A thermostatic element in the form of atube bent into an arc and having its sides at the inner and outer sides of the are each formed with an outer layer of material having one coeflicient of expansion and with an inner layer of material having a smaller coefiicient of expansion, and

having the more rounded portions of its wall pansion, and having less sharply curved portions of its wall formed with inner and outer layers of materials having respectively smaller and larger coefiicients of expansion.

16. A thermostatic element in the form of a section of a tube of elliptical cross section having the more sharply curved portions of its wall each formed with an inner layer of material having one coefficient of expansion and an outer layer of material having a smaller coefficient of expansion and having its less sharply curved wall portions each formed with an inner layer of material having one coeflicient of expansion and an outer layer of material having a greater coeflicient of expansion.

NORMAN L. DERBY. 

